OK so your point is our society now condemns this kind of behaviour, I agree and I would say this was the case even in the 60s - DV is not right.
However, we still celebrate the likes of George Best as a legend of this club to the current day and even have a statue of him in front of OT. So we reject one wife beater who is currently employed at the club and have a statue for another, but that's OK because he's a former player and a heck of a player at that - I just personally think that's a bit hypocritical if we are trying to present ourselves as a champion of women's rights?
I think everyone deserves a chance to redeem themselves. The player in question spent two years away from football, if we want to pursue financial penalties as well sure we can give his entire two years of earnings to a DV charity, make him apologise for his behaviour in public and issue a joint statement with his partner - serve additional time away from football as well if he wants to play in the premier league, or even make him contribute half of his future earnings at Manchester United to a DV charity if he wants to play for United. Other than that, there is nothing else Manchester United can demand from him (If they want to keep him, or of course they can get rid of him) given his partner doesn't want to press charges, and if they are also not willing provide an explanation for what happened should we not let the club execs decide whether he plays or not (Based on what the internal investigation revealed), and also respect whatever decision they make, and also not pressure them towards making a certain type of decision that sits favourably with a certain side of the fanbase (Based on evidence for which the fanbase does not have full context)?
I'm not trying to be a contrarian for the sake of it and I will respect whatever decision the club makes in the end - just saying that this is not a black and white issue as is the case with many things in this world.